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Canadian Arctic ice outpacing global melt average: study

American researchers suggest the melting season for Arctic sea ice is growing faster across much of the Canadian Arctic than anywhere else in the world.

A recently published article outlines how they used satellite microwave data to measure when sea ice begins to melt in the spring and when it starts refreezing in the fall. The researchers were able to look with 99 per cent accuracy as far back as 1979 and examine the entire circumpolar globe, the first time scientists have been able to do so.

They found that, on average, sea ice has started melting 2.5 days earlier every decade and begun to refreeze 3.7 days later. That means the average melt season is just under 20 days longer than it was 30 years ago.

"All areas in the Arctic show a trend toward earlier melt onset and also a trend toward later freeze-up," says the paper, published in the latest Journal of Geophysical Research.

However, the melt period for ice in several areas of the Canadian Arctic is growing even faster.

In Baffin Bay, at the eastern gate of the Northwest Passage, it is increasing about 20 per cent faster than the global average. And in the Beaufort Sea and Hudson Bay, the melt period is now a full month longer than it was in 1979.

In fact, the melting season for Hudson Bay ice is increasing at one of the fastest paces in the world, probably because it's one of the most southerly ice packs.

The only Canadian melt period increasing at the global average was found in ice tucked in between the High Arctic islands.

The study couldn't answer why the Canadian ice melt periods were growing faster than some in Russian waters.

The data will allow scientists to get a better handle on the feedback effects of climate change, said Julienne Stroeve, a scientist at the U.S. National Snow and Ice Data Centre and one of the report's co-authors. The longer Arctic seas remain open, the more energy from the sun they are able to absorb – further delaying their freeze-up.

"The open waters have a longer time in the summer to absorb solar radiation, which is a positive feedback that helps melt more and more ice," Stroeve said.

That seems to be what's happening. Data shows most of the prolonged melt season is occurring because water is freezing later in the fall rather than earlier in the spring.

The findings have wide-ranging implications for everything from economic development to animal habitat. Miners are already looking ahead to using northern waters to move mineral ores. Energy companies have begun laying plans to exploit offshore oil and gas reserves in once ice-choked waters.

But animals such as polar bears and seals depend on sea ice. Biologists have already noted significant declines in the condition of bears in the Hudson Bay area.

Stroeve said her team's findings are consistent with a larger pattern occurring everywhere in the Arctic.

"There's great evidence that there's something happening on the planet. All the changes that we're seeing, whether it's on the sea ice or the Greenland Ice Sheet or overland, it's consistent with this big warming trend."

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